A2A vs MCP vs AP2 vs UCP
Four AI agent standards, compared in plain English
Quick answer: MCP connects an AI assistant to tools and data. A2A lets AI agents talk to each other. AP2 lets an agent pay with proof of what the customer approved. UCP lets shopping agents browse and buy from online shops.
At a glance
- MCP (Model Context Protocol): connects an assistant to your tools and data. Introduced by Anthropic in late 2024.
- A2A (Agent2Agent): lets agents discover and message each other. Launched by Google in 2025, now under the Linux Foundation.
- AP2 (Agent Payments Protocol): lets agents pay, with signed mandates as proof. Announced by Google in September 2025.
- UCP (Universal Commerce Protocol): lets shopping agents read a catalogue and check out. Announced by Google in January 2026, co-developed with Shopify.
Which one answers which question?
- “Can an assistant look up my live stock or opening hours?” MCP.
- “Can a customer’s agent ask my business for a quote?” A2A.
- “Can an agent pay and can I prove the customer agreed?” AP2.
- “Can an AI shopping agent buy from my online shop?” UCP.
Which does a UK business need?
Most need one or two, not all four.
- Service business (trades, clinics, salons): A2A, maybe MCP.
- Online shop: UCP first, then AP2 when payments by agents are common.
- Any business: clean structured data, an llms.txt file and accurate facts. This is the base for all four.
How they work together
A customer’s agent finds you (A2A), reads your live data through a connected assistant (MCP), agrees a purchase (UCP) and pays with proof of consent (AP2). Each standard does one job. They are designed to fit together.
Keep the order right
All of this is new and still changing. Do the basics first with our readiness checklist or run the free scan on the homepage, then add protocols where they bring a real benefit.
Frequently asked questions
Is MCP a competitor to A2A?
No. They solve different problems. MCP is for tools and data. A2A is for agents talking to agents.
Do I need all four?
Almost never. Pick the ones that match what your customers will ask an AI to do.
Which should I start with?
Start with accurate structured data and a clear website, then the one protocol that matches your business.
Are these standards final?
No. They are new and evolving, so we check each current specification before building.
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